1. Field of the Invention
This invention relates to support structures for dynamoelectric machine stator coils, and more particularly, to support structures for spiral pancake stator coils.
2. Description of the Prior Art
Air gap stator windings were developed and adapted for use in a variety of dynamoelectric machines including generators having a superconducting field winding. Spiral pancake stator winding configurations utilize individual coils which spiral outwardly from a radially inner stator boundary to a radially outer stator boundary. Such winding configuration has certain advantages and is particularly effective in providing radial and tangential securement for each of the electrical coils. Such windings are illustrated in Austrian Pat. No. 329,670 having an effective date of May 25, 1976, and U.S. Pat. No. 4,151,433, issued Apr. 24, 1979 in the name of Mr. C. Flick and assigned to the Electric Power Research Institute. In addition to the relative coil disposition in the spiral pancake stator winding the latter patent application illustrates a liquid cooling scheme particularly adapted to such spiral pancake winding.
Through a series of wedges distributed adjacent the coils and interposed between radially inner and outer structural members, the coils, as separate units, were effectively mechanically supported. Individual coil sides or turns are serially connected and concentrically arranged to form the coils. Such individual coil turns are sometimes subjected to continuous vibration in addition to high electromagnetic forces during fault condition operation. Exposure of individual coils to such forces necessitate uniform support for each of the coils as a unit and for each of the coil turns individually. In section 3 of an article entitled "New Solutions For The Design Of Large Turbo Generators Up To 2GVA, 60KV" by Aichholzer, Eingelangt, 9-25-74, the following was included: . . . "the naturally occurring space in the center of each concentric pancake coil can be partially filled with ferromagnetic material, which leads to a reduction of the effective gap and thus to reduced excitation requirements." As stated, the ferromagnetic material was disposed in the center of each pancake coil in an unspecified manner so as to reduce excitation requirements. Forming the coils of a stator winding into a monolithic structure by injecting impregnating and bonding resins thereamong has also been suggested for stiffening the coils and supporting individual conductor turns. While such resins may, under appropriate circumstances, effectively brace the individual coil turns, monolithic structures subjected to extended service in dynamoelectric machines having high mechanical and electromagnetic force levels have not proven highly successful.